Pump structure for self-adjusting hydropneumatic suspensions

ABSTRACT

A miniature hydraulic pump, especially for automotive selfleveling vehicle suspensions using electric drive motors, in which the intake passage between the intake valve and the pumping chamber is split into two bores which communicate with the intake valve chamber on opposite sides of a ball check. The portion of the intake passage turned toward the pumping chamber is sectorally divergent away from the pumping chamber and lies in a plane perpendicular to the axis of the plunger and the pumping chamber.

United States Patent Inventor Erich Hahn Ennepetal-Buttenberg, GermanyAppl. No. 875,642 Filed Nov. 12, 1969 Patented Oct. 5, 1971 AssigneeFirms August Bllstein Ennepetal-Altenvoirde, Germany Priority Nov. 12,1968 Germany P 18 08 549.9

PUMP STRUCTURE FOR SELF-ADJUSTING HYDROPNEUMATIC SUSPENSIONS 7 Claims, 3Drawing Figs.

U.S.Cl. 417/569 lnt.Cl F041: 21/02 Field 01 Search 417/569,

[56] References Cited UNITED STATES PATENTS 1,120,635 12/1914 Vidar417/569 1,489,452 4/1924 Napolis et a1. .1 417/569 2,690,278 9/1954Bacheller 417/567 X Primary Examiner-Robert M. Walker Attorney-Jim! F.Ross PATENTEU BET 5157:

PUMP STRUCTURE FOR SELF-ADJUSTING HYDROPNEUMA'IIC SUSPENSIONS My presentinvention relates to a hydraulic pump and, more particularly, to ahydraulic pump for level-regulating hydropneumatrc suspensions.

It has become increasingly important in recent years to provideautomatic level regulation of the body of an automotive vehicle withrespect to the undercarriage thereof and, accordingly, numerousload-leveling or body-leveling devices have been provided for thispurpose.

An automotive vehicle, e.g. a truck or automobile, generally comprises achassis or body from which the wheel structures are resilientlysuspended, shock-absorbing damper devices being provided in conjunctionwith springs between the wheel assemblies and the chassis or body. Ifthe spring constant is unchanged with increasing load upon the bodythere occurs a downward displacement of the chassis or body relative tothe wheel structure which may be disadvantageous. The damper andshock-absorbing devices, however, may include hydropneumatic chambersfunctioning in part as springs resisting the downward displacement ofthe chassis or body under load. There have been provided heretoforepumping arrangements adapted to increase the pressure in ahydropneumatic compartment in such systems to raise the body to apredetermined level in spite of loading.

in certain systems for this automatic level regulation of a vehiclebody, a plunger connected to one of the dashpot members may bereciprocated in a cylinder connected with the other, in the course ofthe normal oscillations of the wheel assemblies and the body duringvehicular motion. The pumping action may be controlled by a valveadapted to establish the proper level of the body. In still anotherarrangement for this purpose an electrically driven pump is set inoperation to supply the fluid pressure necessary to restore the bodylevel in the event of loading to reduce the level.

In my commonly assigned copending application Ser. No. 828,297, forexample, I have described and claimed a selfleveling hydropneumaticsuspension unit adapted to operate even when the vehicle is stationary.

The suspension-unit housing in this case includes an electric motordriving a pump as well as a regulating valve. A level control switchelectrically operates the motor and the valve in dependence upon thevehicle load.

More specifically, the hydropneumatic suspension includes an elongatedunit having a piston of the dashpot adapted to be connected to one ofthe vehicle members (e.g. the vehicle body) and a cylinder within whichthe dashpot piston is reciprocable and connected to the other vehiclemember, e.g. a wheel assembly. Below this working chamber or cylinder,which is filled with a liquid, I provide an electrically driven pumpadapted to displace liquid from a reservoir chamber into the workingcylinder. A regulating valve is arranged to control the flow of fluidfrom the working cylinder to the reservoir chamber and an electric motorforms part of the suspension unit and is controlled by a level-sensingswitch connected between the motor and an energy source such as thevehicle battery. The pump is formed in the base of the working cylinderand has a number of radial passageways in each of which a pumpingplunger is displaceably mounted. Each of the plunger: has a head at itsradially inner end which is biased by a spring into contact with the endof a cam shaft whose cam surfaces are eccentric and are driven by themotor mounted beneath the base plug. The radially outer ends of thepassageways form relatively small pump chambers which are connected withthe working chamber of the dashpot by outlet channels fitted withnonreturn or check valves.

In automatic level-regulating devices for automotive vehi cles in whichan electric motor is provided to drive a pump, it is necessary tominimize the size of the pump assembly and, consequently, to operatewith relatively short pumping strokes to allow the system to beassembled as part of the hydropneumatic suspension and keep the massassociated with the oscillating wheel assemblies as small as possible.Thus the volume of each stroke of a piston pump of this character isrelatively small and, to obtain a significant displacement, the pistonor plunger must be reciprocated at a high rate.

Because of the relatively small pumping chamber and volume per stroke,the ports, ducts or passages connecting the pumping chamber with thedischarge valve and the intake valve must be proportionately short andof narrow cross section. The pump requirements are a result of the factthat the size must be kept small, that the pump must be capable ofovercoming the pressure within the shock-damping cylinder, and that thepressure in the hydraulic supply chamber must be kept as low aspossible.

As a result of the narrow dimensions of the pumping chamber and thepassages leading to the valves, cavitation affccts and/or foaming areencountered in the fluid which is displaced. The emulsification andfoaming action is extremely disadvantageous in that gas bubbles areformed within the working chamber, thereby limiting the efficiency ofthe pump since the trapped gases may expand and contract with eachpumping stroke without displacement of fluid, especially when the pumpstroke is short and the plunger is oscillated at high rates. Thecapillary effects tend to retain the gas bubbles or accumulations in theslender channels and thereby also limit the intake offluid into thepumping chamber.

in general, therefore, these disadvantages can be attributed to therelatively long but relatively narrow channels between the intake andoutlet valves and the pumping chamber, and especially in the intakepassage running from the intake valve to the pumping chamber. it is not,however, a simple matter to enlarge the intake passage since suchenlargement increases the displacement requirements prior to valveclosure and has hitherto required greater pump strokes or pump-chambervolumes.

it is, therefore, the principal object of the present invention toprovide an improved hydraulic pump of the plunger type in which theaforementioned disadvantages are obviated and the effect offoaming/cmulsification and entrapment of gases is markedly reduced oreliminated.

it is another object of this invention to provide a pump arrangement incombination with a self-adjusting hydropneumatic suspension which is ofincreased efficiency by comparison with earlier pump arrangements andyet need not be of increased dimensions.

Still further, it is an object of this invention to provide an improvedhydraulic pump for a self-adjusting hydropneumatic suspension forautomotive vehicles which extends the principles set forth in thecopending application mentioned earlier.

These objects and others which will become apparent hereinafter areattained in accordance with the present invention in a hydraulic pumpfor the purposes described which, in spite of its small dimensions andthe concomitantly narrow pumping chamber, it more effective than theearlier systems by providing an automatic venting of the pump chamber,thereby releasing any gas accumulations which may be present therein.

More specifically, the hydraulic pump of the present invention isprovided with a relatively small cross section pumping chamber in whicha plunger is reciprocable, but which has an intake passage whose sideturned toward the intake-valve chamber is of lesser cross section thanthe side turned toward the pumping chamber, the passage opening into theintake port on opposite sides of the intake-valve body. Advantageously,the intake passage has a portion turned toward the pump chamber whichwidens in sector configuration toward the valve chamber and is splitinto two bores opening on opposite sides of the intake valve body asnoted earlier. The intake valve, according to this invention, is a ballcheck valve adapted to seat against a frustoconical surface surroundingthe intake port which may have a cross section substantially less thanthe collective cross sections of the two bores or substantially equal tothe cross section of the pumping chamber.

Between the two bores and in axial alignment with the intake port, so asto provide an abutment surface for the ball check, I provide a member orwall which subdivides the intake passage between the check valve chamberand the pumping chamber, the check valve chamber having a cross sectiongreater than the collective cross sections of the two bores andnarrowing via the frustoconical seat to the intake port.

The aforedescribed structure has been found, in practice, to eliminatethe disadvantages of earlier hydraulic pump systems. Thus, when the pumpplunger is oscillated back and forth at a high rate, there isestablished a circulation of hydraulic fluid into the intake port aroundthe ball check and toward the upper part of the valve chamber. Any teamor emulsified hydraulic fluid appears to rise to the top of the sectoralchamber and, by virtue of its outwardly divergent configuration passesupwardly to the upper bore of the twin bores opening into the valvechamber. Surprisingly, in spite of the fact that hydraulic fluid isdrawn into the intake port, accumulated gases pass over the ball checkand through the intake port in the opposite direction, therebycompleting the circulation path. Whereas earlier pumping arrangementsresulted in entrapment of gas bubbles in the intake passage soon aftercommencement of operation, so that subsequent plunger strokes merelyresulted in compression and expansion of the entrapped gases, the systemof the present invention appears to give rise to a circulation of gasesout of the pumping chamber and the valve chamber. By virtue of therelationship of the two bores to the sectoral shape of their manifoldand to the ball check of the intake valve, pumping proceeds withoutentrapment of gas bubbles and reduction in pumping deficiency and, inspite of the fact that gas is vented from the valve chamber, hydraulicfluid appears to enter without noticeable impediment. While the intakevalve port is relatively narrow as indicated earlier, a forward movementof hydraulic fluid and an opposite movement of entrained gases are foundto take place in the respective bores so that pumping remainsunobstructed. As the gases are passed into the valve chamber, they ventinto a low-pressure reservoir from which the hydraulic fluid is drawn.

According to still another feature of this invention, the intake-valveseat is provided along its side turned away from the valve chamber andin the direction of the low-pressure reservoir with a frustoconicallydivergent recess aligned with the frustoconical seat and of acorresponding apex angle, the frustoconical recess being coaxial withthe frustoconical seat and the circular intake port between them. Itappears that the approved results obtained with this modification are inpart derived from the fact that the length of the channel between theintake chamber and the low-pressure hydraulic fluid reservoir is reducedto a minimum so that no air entrapment can occur in this chamber.Furthermore, the frustoconical shape of the recess insures movement ofany vented air away from the intake flow path.

The above and other objects, features and advantages of this inventionwill become more readily apparent from the following description,reference being made to the accompanying drawing in which:

FIG. 1 is an axial cross-sectional view through a hydraulic pumpembodying the principles of this invention;

FIG. 2 is a cross section taken along the line llll of FIG. 1, but drawnto a greater scale; and

FIG. 3 is a view partially in elevation and with parts broken awayindicating the relationship of the hydraulic pump of this invention to asystem for the automatic control of the level of a vehicle body inresponse to loading.

In my copending application mentioned earlier, there are describednumerous arrangements in which an electric motor M is provided with aneccentric shaft arrangement E designed to reciprocate the plungers P1and P1 of a pair of one or more pumps P of the type shown in FIGS. 1 and2. The motor M is controlled by a level-control switch S which may alsooperate a valve system capable of bleeding the hydraulicallypressurizable damper D into which the hydraulic fluids is fed underpressure. The discharge port 9" of the pump P is here shown tocommunicate with the load leveler chamber D while the bore 3 of the pumpP registers with a suitable port opening into the low-pressure reservoirR. When the switch means S operates the control valve to bleed the loadleveler D, hydraulic fluid returns to the reservoir R. From FIG. 3 itwill be apparent that the pump assembly P is extremely small and may beof half of the size represented in FIG. 1.

The miniature hydraulic pump shown in FIGS. 1 and 2 comprises a massivepump housing 1 formed with a longitudinally expanding bore 2 having asmall-diameter portion 2a separated by a step 2' from a large diameterportion 2b and extending at right angles to a bore 3 terminating in anend wall 22 which separates the large diameter portion 2b from the bore3.

The pump cylinder 4 is received within the bore 2 and is constituted asa cylindrical member having three steps, including a small diameteraxially extending cylindrical boss 4a at one end projecting from thehousing 1 and forming a centering member for a helicoidal compressionspring 8 surrounding a pumping plunger 7 and seated against the head 7'thereof.

Inwardly of the cylindrical boss 40, the cylinder 4 is provided with acylindrical shank 4b of intermediate diameter, closely fitting in step20 of the bore 2. The large diameter step 4c of the cylinder bearsagainst the shoulder 2' and prevents further movement of the cylinder 4to the right once the cylinder is inserted in the direction of arrow Ainto the bore 2.

Within the cylinder 4, there is provided the cylindrical Iongitudinalbore 5 which extends through the cylinder and slidably receives theplunger 7 so as to define therewith a generally cylindrical pumpingchamber 6. At its free end, the plunger 7 has a convex head 7'conforming generally to a spheroidal surface and engageable with aneccentric or cam of an electric motor for reciprocation of the plungeras described in connection with FIG. 3. The spring 8 urges the plunger 7to the right and is compressed by the eccentric.

An insert disk 9, preferably composed of a wear-resistant syntheticresin, such as polytetrafluoroethylenc, is received in the large step 2bof the bore 2 and forms a cage for the discharge valve. An annular seal10 is received in a peripheral groove 10a of the cage 9 and sealinglyengages the wall of the bore 2 to prevent leakage of fluid between thepump chamber and the discharge chamber 13. The body 9 is formed with adischarge port 9" communicating between the chamber 13 and the pumpingchamber 6 and terminating in a frustoconical valve seat 9'. The lattercooperates with the conical tip 1 In of a valve member 11 axiallyaligned with the plunger 7 and urged into the seat 9' by a compressionspring 12 seated against the rear wall of the insert 9. This rear wallis provided with a discharge opening 9" through which hydraulic fluidmay be forced into the hydropneumatic pressure chamber of theload-leveling cylinder.

In the intake bore 3, which communicates with the reservoir of theself-leveling suspension, I provide the intake valve 14 which comprises,as best seen in FIG. 2, a valve seat 15 in the form of a disk which mavbe composed of a wear-resistant synthetic resin, such aspolytetrafluoroethylene. In an annular groove 204 along the externalperiphery of this body 15, there is provided an elastomeric sealing ring20 preventing communication between the intake valve chamber l7 and thechannel 3 connecting this chamber with the reservoir.

The disk 15 is centrally provided with a valve bore 16, also referred toherein as the intake port, the valve bore having a length d in thedirection of fluid flow which is made small by comparison with the axialthickness of the disk 15. To this end, the side of the disk 15 turnedaway from the intake valve chamber is formed with a frustoconical recess15" coaxial with the bore 16 and terminating therein, the recesswidening outwardly from this bore. The valve seat 15', also coaxial withthe bore 16 and the recess 15'', may be of similar conicity and isturned toward the valve chamber [7. The valve chamber 17 is defined by aring 19 inserted between the wall 22 and the disk 15 and provided with acentral opening 17' of a diameter equal to the maximum diameter of thefrustoconical valve seat This diameter is less than that of a ball check18 received in the bore and limited in its axial movement away from thevalve seat Is by the wall 22 which is formed with a central portion 12adapted to constitute an abutment for the ball 18. The ball and theabutment 22, 22' lie in a plane perpendicular to the axis of the bore 16and the seat 15'. When the pump pressure builds up behind the ball 18,the latter is urged in the direction of arrow B into engagement with theseat 15' to block outflow of the hydraulic fluid into the reservoir fromthe pumping chamber 6. The bore 16 has a cross section not substantiallygreater than the cross section of the valve chamber 6 and possibly, asshown in FIG. 1, smaller than the cross section of the pump chamber.

Between the valve chamber 17 of the pump chamber 6, l provide an intakepassage which is generally indicated by the reference numeral 21. Theintake passage comprises, at its end proximal to the valve chamber 6, asectoral portion 21" converging radially inwardly to the discharge port9" but with a spread corresponding to the diameter of the discharge port9" as will be apparent from FIG. 1. The sectoral portion 21" may beformed in the end of the insert body 9 abutting the pumping cylinder 4.

At its end communicating with the valve chamber 17, the intake passage21 is split between a pair of axially extending bores 21' and M" whichflank the axis C of the intake chamber and open into the latter onopposite sides of the ball 18 and the abutment surface 22' thereof. Thebores 21' and 2] are spaced apart to correspond to the maximum spread sof the sectoral portion 21" and the maximum diameter 1 of the bore 17'.

Upon reciprocation of the piston or plunger 7 by the eccentric and theelectric motor described above, the motor being driven from the vehiclebattery under the control of a levelsensing switch, fluid is alternatelydrawn through the port 16 and expelled at an elevated pressure throughthe port 9". During this process, forming of the hydraulic fluid mayoccur but it is found that a circulation is established around the ballwhereby the gases may pass from the pumping chamber upwardly through thesectoral portion 21" and eventually are vented through the port 16, aspreviously described.

The improvement described and illustrated is believed to admit of manymodifications within the ability of persons skilled in the art, all suchmodifications being considered within the spirit and scope of theinvention except as limited by the appended claims.

lclaim:

l. A hydraulic pump comprising a housing forming a pump cylinder, aplunger reciprocable in said cylinder and defining a pump chambertherein, an intake valve communicating with a source of hydraulic fluidand connected with said chamber for delivering hydraulic fluid to saidchamber, an outlet valve connected with said chamber for discharginghydraulic fluid under pressure therefrom and an intake passage formed insaid housing and connecting said intake valve with said valve chamber,said passage having a larger cross section in the direction of saidintake valve and a smaller cross section in the direction of said pumpchamber, said intake valve including an intake port and a valve bodyadapted to block said port, said intake passage being bifurcated andopening in the direction of said intake port toward opposite sides ofsaid body, said intake passage having a generally sectoral portionwidening away from said pump chamber and lying in a plane perpendicularto the axis of said cylinder and said plunger, and a bifurcated portioncommunicating with said sectoral portion and constituted by a pair ofmutually parallel bores formed in said housing, said intake valvedefining in said housing an intake chamber communicating with said portand receiving said body, said body being formed as a ball received insaid intake chamber, said bores opening into said intake chamber toeither side of said ball.

2. The hydraulic pump as defined in claim 1 2h343 in said intake valveincludes a valve member provided with said intake port and partiallyforming said intake chamber, said member being formed along its sideturned toward said intake chamber with a frustoconical valve seatengageable with said ball and converting toward said port, and beingformed along its side turned away from said intake chamber with afrustoconica] recess widening outwardly from said port and coaxialtherewith.

3. The hydraulic pump defined in claim 2 wherein said housing isprovided with a stepped bore, said cylinder being received in saidstepped bore, said outlet valve comprising an insert received in saidstepped bore and abutting said cylinder while defining therewith saidsectoral portion of said intake passage.

4. The hydraulic pump defined in claim 3 wherein said insert is composedof a wear-resistant synthetic resin and is formed in a side oppositesaid pump chamber with a frustoconical valve seat, said outlet valveincluding a conically pointed valve member received in said insert andspringbiased into the seat formed in said insert.

5. The hydraulic pump defined in claim 4 wherein said plunger has a freeend projecting from said housing, said pump further comprising springmeans seated against said housing and bearing against said free end andfor yieldably urging same away from said housing.

6. The hydraulic pump defined in claim 5 wherein said free end has arounded head forming a seat for said spring means and engageable with aneccentric assembly for reciprocating said plunger.

7. The hydraulic pump defined in claim 6, further comprising an electricmotor for driving said eccentric assembly and reciprocating saidplunger.

2. The hydraulic pump as defined in claim 1 2h343 in said intake valveincludes a valve member provided with said intake port and partiallyforming said intake chamber, said member being formed along its sideturned toward said intake chamber with a frustoconical valve seatengageable with said ball and converting toward said port, and beingformed along its side turned away from said intake chamber with afrustoconical recess widening outwardly from said port and coaxialtherewith.
 3. The hydraulic pump defined in claim 2 wherein said housingis provided with a stepped bore, said cylinder being received in saidstepped bore, said outlet valve comprising an insert received in saidstepped bore and abutting said cylinder while defining therewith saidsectoral portion of said intake passage.
 4. The hydraulic pump definedin claim 3 wherein said insert is composed of a wear-resistant syntheticresin and is formed in a side opposite said pump chamber with afrustoconical valve seat, said outlet valve including a conicallypointed valve member received in said insert and spring-biased into theseat formed in said insert.
 5. The hydraulic pump defined in claim 4wherein said plunger has a free end projecting from said housing, saidpump further comprising spring means seated against said housing andbearing against said free end and for yieldably urging same away fromsaid housing.
 6. The hydraulic pump defined in claim 5 wherein said freeend has a rounded head forming a seat for said spring means andengageable with an eccentric assembly for reciprocating said plunger. 7.The hydraulic pump defined in claim 6, further comprising an electricmotor for driving said eccentric assembly and reciprocating saidplunger.